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letter 13047
ZINC PLATING AND OLIVE BLACK
PASSIVATION (CHROMATING)
Hello everyone,
Can anybody clear my query as given below.
After Zinc plating & Olive black passivation on steel
fasteners & fine blanked components (structural steel which are
copper brazed with En8 material):
1. We face the problem on colour inconsistency - olive black not
proper.
2. Also colour retentivity ( i.e. after few days olive black turns
complete black).
3. Blister formation.
4. What should be the surface finish in the component.
5. What is the optimum plating thickness.
6. We require brake fluid compatibility( DOT3 & DOT 4 ).
7. What are the chemicals,their percentage etc. required to overcome
the above problems.
8. How far the intricate components get affected compared to plane
surfaces.
9. What is the expected life of components in NSS test.
Senthil Deepak Nandakumar
- Coimbatore, Tamil Nadu, India
Mr.Nandakumar,
This site is a place where peers exchange information and work
together towards solving finishing problems. You've not yet helped
anyone else with their inquiries, while your inquiry has 9 different
broad-ranging requests. I mention this not as criticism, but to
explain why inquiries like yours usually go unanswered. People just
feel very little sense of obligation to help a person go into
successful competition against them when that person presents himself
as knowing nothing about metal finishing :-)
What proprietary olive black chromate or home brew formula do you
use now? What kind of zinc plating do you do now--acid, alkali, or
cyanide? What is the surface finish now? What thickness do you plate
now? Do you have brake fluid compatability now? What thickness ratio
do you get between the HCD and LCD areas now? What NSS life do you
get now? Thanks.
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Ted Mooney, P.E.
finishing.com
Brick, New Jersey
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The plating system has two main parts to it: the main zinc
plating, and the passivation. The thickness of the plating depends on
your application. The auto parts we work with get around 8 microns of
plating. The passivate is not specified by thickness.
Some of these technical issues should be addressed with your
plating supplier. They should understand their processes well and
should be able to educate you a bit on issues like this. You can also
refer to the Metal Finishing
Guidebook from Metal Finishing Magazine. This guidebook gives
generic technical explanations of plating and of conversion coatings
(passivation).
Sometimes is is very hard to produce an exact color consistantly.
The color is dependant on the passivation, not necessarily the
plating part. As you make part after part, the chemicals in the bath
deplete, and the concentrations change over time. It can be difficult
to maintain the passivation chemical bath the same all day every day.
You may want to relax your color requirements to make things much
easier for your plater. The plater may not have the capability to
meet tight color requirements.
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Tim Neveau
Rochester Hills, Michigan
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Dear Reader, please --
- Post a
question on a different
subject.
-
- Answer or follow-up on this
subject (in non-commercial
fashion).
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